﻿// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using System.Diagnostics.CodeAnalysis;
using Microsoft.EntityFrameworkCore.Query.SqlExpressions;

namespace Microsoft.EntityFrameworkCore.Query.Internal;

/// <summary>
///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
///     the same compatibility standards as public APIs. It may be changed or removed without notice in
///     any release. You should only use it directly in your code with extreme caution and knowing that
///     doing so can result in application failures when updating to a new Entity Framework Core release.
/// </summary>
public class SelectExpressionPruningExpressionVisitor : ExpressionVisitor
{
    /// <summary>
    ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
    ///     the same compatibility standards as public APIs. It may be changed or removed without notice in
    ///     any release. You should only use it directly in your code with extreme caution and knowing that
    ///     doing so can result in application failures when updating to a new Entity Framework Core release.
    /// </summary>
    [return: NotNullIfNotNull("expression")]
    public override Expression? Visit(Expression? expression)
    {
        switch (expression)
        {
            case ShapedQueryExpression shapedQueryExpression:
                return shapedQueryExpression.Update(
                    ((SelectExpression)shapedQueryExpression.QueryExpression).Prune(),
                    Visit(shapedQueryExpression.ShaperExpression));

            case RelationalSplitCollectionShaperExpression relationalSplitCollectionShaperExpression:
                return relationalSplitCollectionShaperExpression.Update(
                    relationalSplitCollectionShaperExpression.ParentIdentifier,
                    relationalSplitCollectionShaperExpression.ChildIdentifier,
                    relationalSplitCollectionShaperExpression.SelectExpression.Prune(),
                    Visit(relationalSplitCollectionShaperExpression.InnerShaper));

            case DeleteExpression deleteExpression:
                return deleteExpression.Update(deleteExpression.SelectExpression.Prune());

            case UpdateExpression updateExpression:
                return updateExpression.Update(
                    updateExpression.SelectExpression.Prune(),
                    updateExpression.ColumnValueSetters.Select(e => new ColumnValueSetter(e.Column, (SqlExpression)Visit(e.Value)))
                        .ToList());

            default:
                return base.Visit(expression);
        }
    }
}
